net/ipv4/netfilter/iptable_mangle.c

   1 /*
   2  * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
   3  *
   4  * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
   5  * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * Extended to all five netfilter hooks by Brad Chapman & Harald Welte
  12  */
  13 #include <linux/config.h>
  14 #include <linux/module.h>
  15 #include <linux/netfilter_ipv4/ip_tables.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/skbuff.h>
  18 #include <net/sock.h>
  19 #include <net/route.h>
  20 #include <linux/ip.h>
  21
  22 MODULE_LICENSE("GPL");
  23 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  24 MODULE_DESCRIPTION("iptables mangle table");
  25
  26 #define MANGLE_VALID_HOOKS ((1 << NF_IP_PRE_ROUTING) | \
  27                             (1 << NF_IP_LOCAL_IN) | \
  28                             (1 << NF_IP_FORWARD) | \
  29                             (1 << NF_IP_LOCAL_OUT) | \
  30                             (1 << NF_IP_POST_ROUTING))
  31
  32 /* Ouch - five different hooks? Maybe this should be a config option..... -- BC */
  33 static struct
  34 {
  35         struct ipt_replace repl;
  36         struct ipt_standard entries[5];
  37         struct ipt_error term;
  38 } initial_table __initdata
  39 = { { "mangle", MANGLE_VALID_HOOKS, 6,
  40       sizeof(struct ipt_standard) * 5 + sizeof(struct ipt_error),
  41       { [NF_IP_PRE_ROUTING]     = 0,
  42         [NF_IP_LOCAL_IN]        = sizeof(struct ipt_standard),
  43         [NF_IP_FORWARD]         = sizeof(struct ipt_standard) * 2,
  44         [NF_IP_LOCAL_OUT]       = sizeof(struct ipt_standard) * 3,
  45         [NF_IP_POST_ROUTING]    = sizeof(struct ipt_standard) * 4 },
  46       { [NF_IP_PRE_ROUTING]     = 0,
  47         [NF_IP_LOCAL_IN]        = sizeof(struct ipt_standard),
  48         [NF_IP_FORWARD]         = sizeof(struct ipt_standard) * 2,
  49         [NF_IP_LOCAL_OUT]       = sizeof(struct ipt_standard) * 3,
  50         [NF_IP_POST_ROUTING]    = sizeof(struct ipt_standard) * 4 },
  51       0, NULL, { } },
  52     {
  53             /* PRE_ROUTING */
  54             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  55                 0,
  56                 sizeof(struct ipt_entry),
  57                 sizeof(struct ipt_standard),
  58                 0, { 0, 0 }, { } },
  59               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  60                 -NF_ACCEPT - 1 } },
  61             /* LOCAL_IN */
  62             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  63                 0,
  64                 sizeof(struct ipt_entry),
  65                 sizeof(struct ipt_standard),
  66                 0, { 0, 0 }, { } },
  67               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  68                 -NF_ACCEPT - 1 } },
  69             /* FORWARD */
  70             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  71                 0,
  72                 sizeof(struct ipt_entry),
  73                 sizeof(struct ipt_standard),
  74                 0, { 0, 0 }, { } },
  75               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  76                 -NF_ACCEPT - 1 } },
  77             /* LOCAL_OUT */
  78             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  79                 0,
  80                 sizeof(struct ipt_entry),
  81                 sizeof(struct ipt_standard),
  82                 0, { 0, 0 }, { } },
  83               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  84                 -NF_ACCEPT - 1 } },
  85             /* POST_ROUTING */
  86             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  87                 0,
  88                 sizeof(struct ipt_entry),
  89                 sizeof(struct ipt_standard),
  90                 0, { 0, 0 }, { } },
  91               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  92                 -NF_ACCEPT - 1 } },
  93     },
  94     /* ERROR */
  95     { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  96         0,
  97         sizeof(struct ipt_entry),
  98         sizeof(struct ipt_error),
  99         0, { 0, 0 }, { } },
 100       { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
 101           { } },
 102         "ERROR"
 103       }
 104     }
 105 };
 106
 107 static struct ipt_table packet_mangler = {
 108         .name           = "mangle",
 109         .valid_hooks    = MANGLE_VALID_HOOKS,
 110         .lock           = RW_LOCK_UNLOCKED,
 111         .me             = THIS_MODULE,
 112         .af             = AF_INET,
 113 };
 114
 115 /* The work comes in here from netfilter.c. */
 116 static unsigned int
 117 ipt_route_hook(unsigned int hook,
 118          struct sk_buff **pskb,
 119          const struct net_device *in,
 120          const struct net_device *out,
 121          int (*okfn)(struct sk_buff *))
 122 {
 123         return ipt_do_table(pskb, hook, in, out, &packet_mangler, NULL);
 124 }
 125
 126 static unsigned int
 127 ipt_local_hook(unsigned int hook,
 128                    struct sk_buff **pskb,
 129                    const struct net_device *in,
 130                    const struct net_device *out,
 131                    int (*okfn)(struct sk_buff *))
 132 {
 133         unsigned int ret;
 134         u_int8_t tos;
 135         u_int32_t saddr, daddr;
 136         unsigned long nfmark;
 137
 138         /* root is playing with raw sockets. */
 139         if ((*pskb)->len < sizeof(struct iphdr)
 140             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {
 141                 if (net_ratelimit())
 142                         printk("ipt_hook: happy cracking.\n");
 143                 return NF_ACCEPT;
 144         }
 145
 146         /* Save things which could affect route */
 147         nfmark = (*pskb)->nfmark;
 148         saddr = (*pskb)->nh.iph->saddr;
 149         daddr = (*pskb)->nh.iph->daddr;
 150         tos = (*pskb)->nh.iph->tos;
 151
 152         ret = ipt_do_table(pskb, hook, in, out, &packet_mangler, NULL);
 153         /* Reroute for ANY change. */
 154         if (ret != NF_DROP && ret != NF_STOLEN && ret != NF_QUEUE
 155             && ((*pskb)->nh.iph->saddr != saddr
 156                 || (*pskb)->nh.iph->daddr != daddr
 157 #ifdef CONFIG_IP_ROUTE_FWMARK
 158                 || (*pskb)->nfmark != nfmark
 159 #endif
 160                 || (*pskb)->nh.iph->tos != tos))
 161                 return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;
 162
 163         return ret;
 164 }
 165
 166 static struct nf_hook_ops ipt_ops[] = {
 167         {
 168                 .hook           = ipt_route_hook,
 169                 .owner          = THIS_MODULE,
 170                 .pf             = PF_INET,
 171                 .hooknum        = NF_IP_PRE_ROUTING,
 172                 .priority       = NF_IP_PRI_MANGLE,
 173         },
 174         {
 175                 .hook           = ipt_route_hook,
 176                 .owner          = THIS_MODULE,
 177                 .pf             = PF_INET,
 178                 .hooknum        = NF_IP_LOCAL_IN,
 179                 .priority       = NF_IP_PRI_MANGLE,
 180         },
 181         {
 182                 .hook           = ipt_route_hook,
 183                 .owner          = THIS_MODULE,
 184                 .pf             = PF_INET,
 185                 .hooknum        = NF_IP_FORWARD,
 186                 .priority       = NF_IP_PRI_MANGLE,
 187         },
 188         {
 189                 .hook           = ipt_local_hook,
 190                 .owner          = THIS_MODULE,
 191                 .pf             = PF_INET,
 192                 .hooknum        = NF_IP_LOCAL_OUT,
 193                 .priority       = NF_IP_PRI_MANGLE,
 194         },
 195         {
 196                 .hook           = ipt_route_hook,
 197                 .owner          = THIS_MODULE,
 198                 .pf             = PF_INET,
 199                 .hooknum        = NF_IP_POST_ROUTING,
 200                 .priority       = NF_IP_PRI_MANGLE,
 201         },
 202 };
 203
 204 static int __init init(void)
 205 {
 206         int ret;
 207
 208         /* Register table */
 209         ret = ipt_register_table(&packet_mangler, &initial_table.repl);
 210         if (ret < 0)
 211                 return ret;
 212
 213         /* Register hooks */
 214         ret = nf_register_hook(&ipt_ops[0]);
 215         if (ret < 0)
 216                 goto cleanup_table;
 217
 218         ret = nf_register_hook(&ipt_ops[1]);
 219         if (ret < 0)
 220                 goto cleanup_hook0;
 221
 222         ret = nf_register_hook(&ipt_ops[2]);
 223         if (ret < 0)
 224                 goto cleanup_hook1;
 225
 226         ret = nf_register_hook(&ipt_ops[3]);
 227         if (ret < 0)
 228                 goto cleanup_hook2;
 229
 230         ret = nf_register_hook(&ipt_ops[4]);
 231         if (ret < 0)
 232                 goto cleanup_hook3;
 233
 234         return ret;
 235
 236  cleanup_hook3:
 237         nf_unregister_hook(&ipt_ops[3]);
 238  cleanup_hook2:
 239         nf_unregister_hook(&ipt_ops[2]);
 240  cleanup_hook1:
 241         nf_unregister_hook(&ipt_ops[1]);
 242  cleanup_hook0:
 243         nf_unregister_hook(&ipt_ops[0]);
 244  cleanup_table:
 245         ipt_unregister_table(&packet_mangler);
 246
 247         return ret;
 248 }
 249
 250 static void __exit fini(void)
 251 {
 252         unsigned int i;
 253
 254         for (i = 0; i < sizeof(ipt_ops)/sizeof(struct nf_hook_ops); i++)
 255                 nf_unregister_hook(&ipt_ops[i]);
 256
 257         ipt_unregister_table(&packet_mangler);
 258 }
 259
 260 module_init(init);
 261 module_exit(fini);